titlesec: \sectionmark breaking \ifthesection?

Question

In the titlesec package, one may use the \ifthesection (or \ifthechapter,...) command to apply some customization commands only when a \section has been defined. However, it seems that using \sectionmark (for instance to define a short running title) breaks this feature. Here is a MWE:

\documentclass{book}

\usepackage[pagestyles,outermarks]{titlesec}
\usepackage{lipsum}

\newpagestyle{main}{ 
\headrule
\sethead[\normalsize \thepage][][\scshape \chaptertitlename~\thechapter. \chaptertitle]
{\ifthesection{\thesection.~\sectiontitle}{}}{}{\normalsize \thepage}
}

\begin{document}

\tableofcontents

\pagestyle{main}

\chapter{First Chapter}
\lipsum
\lipsum

\chapter{Second Chapter}

\section{First Section}
\lipsum
\lipsum

\section{Second Section with a very long title that I do not want to show in the running heads but which is fine for the table of contents}
\sectionmark{Second Section}

\lipsum

\end{document}

In this example, the odd-side headers for chapter 1 (a chapter with no sections) only shows the page number, as expected (in particular the \ifthesection command prevents the dot from showing up):

In chapter 2, we have a first section for which everything works fine:

But things get more complicated when it comes to the second section, which has a very long name. Let us imagine that we want the full name in the table of contents, and a short running head in the headers. The command \sectionmark{Second Section} normally works, but it does not when \ifthesection is used in the headers style definition. In the present form, we get:

I can think of three possibilities to solve this problem:

• One solution would be to remove the \ifthesection command in the headers style definition, but then a dot would appear in the headers for chapters with no sections. Then another way to test if this dot (or any other character) should be printed would be needed.
• Using the optional argument for the \section command: \section[Second Section]{Second Section with a very long title that I do not want to show in the running heads but which is fine for the table of contents}. Then a hack would be needed to modify the table of contents so that the full name appears.
• Playing around with marks to replace the \sectionmark{Second Section} with an appropriate command which does not break the \ifthesection command.

It seems to me that it would be preferable to choose the third solution, the other two looking more like work-arounds. However, I do not know much about the marks system. Does anybody know how to do this?

Answer 1

This is wanted: an explicit \sectionmark command makes \ifthesection false. You can trick titlesec into ignoring this setting by defining a macro similar to \sectionmark that doesn't perform that setting:

\makeatletter
\newcommand{\sectionmarkhead}[1]{%
  \gdef\sectiontitle{#1}%
  \let\ttl@marks\ttl@tm@section
  \ttl@markboth {section}}
\makeatother

If you use \sectionmarkhead{Second section} you'll get the desired result.

Answer 2

If you always want the full name in the TOC (which is solution 2), use the package option toctitles.